Ok, here's one… how do you know that on Cait, it's not the female that has to attract a mate rather than the male? Just because it's the male on Earth, doesn't mean the same holds true elsewhere.
Another: How do you know it's all hair? It could be sensory organs interwoven/protected by hair, that need to dangle from the body (eg because of bio electric interference).

I never saw a need to explain the biology of aliens. The fact that they're alien means they have evolved in a very different environment from us. Who's to say what kinds of features that would cause?